A. Field
The present invention concerns an improved device for cool drying.
B. Related Art
In particular, the present invention concerns a device for cool drying, comprising a heat exchanger whose primary part is the vaporizer of a cooling circuit which also comprises a compressor which is driven by a motor, a condenser, an expansion means between the outlet of the condenser and the inlet of the vaporizer, a control device for controlling the above-mentioned motor and measuring means coupled thereto, whereas the secondary part of the heat exchanger is part of a pipe for the gas to be dried, whereby in this pipe a liquid separator is placed at the outlet of the secondary part of the heat exchanger.
Compressed air supplied for example by a compressor is in most cases saturated with water vapour or has, in other words, a relative humidity of 100%. This implies that, in case of a temperature drop below what is called the dew point, there will be condensation. The condensed water gives rise to corrosion in pipes and tools, and appliances may wear prematurely.
That is why compressed air is dried, which may be done with the above-mentioned device for cool drying. Also other gases may be dried with such a device.
Cool drying is based on the principle that by lowering the air or gas temperature in the vaporizer, moisture in the air or gas will condense, after which the condensed water is separated in a liquid separator and after which the air or gas is heated again, such that this air or gas will be no longer saturated.
The same applies to any other gas than air, and each time we hereafter refer to air, the same also applies to any other gas than air.
A device for cool drying is already known, whereby the above-mentioned measuring means are made as means for measuring the vaporizer pressure or the vaporizer temperature, whereby the cooling circuit is switched on or off on the basis of the measured values coming from said measuring means.
If a take-off of compressed air is recorded, the cooling circuit is started and as soon as the take-off of compressed air stops again, the cooling circuit is stopped again as well.
A disadvantage of such a known device is that the heat exchanger, after the cooling circuit has been switched off, will heat up as there is no cooling any more.
When, subsequently, compressed air is taken off again while the heat exchanger has heated up in the meantime, temperature and dew point peaks may instantly occur in the supplied compressed air, since the gas to be dried in the heat exchanger is not sufficiently cooled then to make the water in said gas to be dried condense at maximum capacity.
A device for cool drying is known as well, provided with a thermal mass, for example in the form of a mixture of water and propylene glycol, for cooling the compressed air.
With such known devices, the cooling circuit is only used for cooling the above-mentioned thermal mass, such that the compressor in this cooling circuit can be switched off as soon as the thermal mass has reached a certain temperature, as a result of which energy can be saved.
A disadvantage of such a known device is that the cooling circuit, due to the presence of the above-mentioned thermal mass, must be made very heavy and sizeable.
Another disadvantage of such a known device is that, due to additional parts such as a reservoir and/or an additional heat exchanger, the construction of the cooling circuit is relatively expensive and complicated and its assembly is very time-consuming.